Patella preparation in total knee arthroplasty procedures is generally performed manually with the use of sawblades and clamps. Calipers may be used during preparation to contact opposing superior and inferior surfaces of the patella to aid in determining the depth of the cut. However, these conventional tools do not adequately control the depth and orientation of the cut which also results in the medial/lateral translational and rotational position of a patellar component.
Patella clamps may be used to clamp the anterior and articular surfaces of the patella before resecting the articular surface of the patella. Additionally, some patella clamps may require fixation pegs or keels to engage the patella before everting it to a desired angle. Common methods to remove bone from the articular surface of the patella include saw resection or milling/planar systems. The removal of bone in either of these systems may provide a flat, stable platform to support, but not secure, a prosthetic patellar component.
The patella includes boney landmarks such as the articular high point, retinaculum and/or the cartilage border. These landmarks may be referenced by a patella clamp to orient the clamp on the non-resected patella in view of a desired final placement of the patellar component. However, these landmarks are generally irregularly shaped, which makes it difficult to orient the clamp below a planned resection level.